Rubber compositions comprising benzoquinones and the use thereof in golf balls

1. A golf ball comprising a core and a cover, wherein the core has at least one layer formed from a rubber composition consisting of:

(a) a base rubber;

(b) at least 0.05 parts by weight of a free radical initiator per 100 parts of the base rubber;

(c) at least 0.15 parts by weight of a benzoquinone per 100 parts of the base rubber;

(d) a coagent selected from the group consisting of metal salts of acrylates, diacrylates, methacrylates, and dimethacrylates;

(e) optionally one or more organosulfur compounds;

(f) optionally one or more particulate fillers; and

(g) optionally one or more processing aids;

wherein a ratio (P BQ /P FRI ) of the amount of the benzoquinone present in the rubber composition (P BQ ), measured in parts by weight per 100 parts of the base rubber, to the amount of free radical initiator present in the rubber composition (P FRI ), measured in parts by weight per 100 parts of the base rubber, is from 0.25 to 0.45; and

wherein the core has a compression of 75 or less and a coefficient of restitution of at least 0.800.

2. The golf ball of claim 1 , wherein the benzoquinone is selected from compounds represented by the following formula, and hydrates thereof:

wherein each R 1 , R 2 , R 3 , and R 4 is independently selected from the group consisting of hydrogen, a halogen group (F, Cl, Br, I), an alkyl group, a carboxyl group (—COOH) and metal salts thereof and esters thereof, an acetate group (—CH 2 COOH) and esters thereof, a formyl group (—CHO), an acyl group, an acetyl group (—COCH 3 ), a halogenated carbonyl group, a sulfo group (—SO 3 H) and esters thereof, a halogenated sulfonyl group, a sulfino group (—SO 2 H), an alkylsulfinyl group, a carbamoyl group (—CONH 2 ), a halogenated alkyl group, a cyano group (—CN), an alkoxy group, a hydroxy group (—OH) and metal salts thereof, an amino group (—NH 2 ), a nitro group (—NO 2 ), an aryl group, an aryloxy group, an arylalkyl group, a nitroso group (—NO), an acetamido group (—NHCOCH 3 ), and a vinyl group (—CH═CH 2 ).

3. The golf ball of claim 1 , wherein the benzoquinone is selected from methyl p-benzoquinone and tetrachloro p-benzoquinone.

4. The golf ball of claim 1 , wherein the rubber composition is substantially free of organosulfur compounds.

5. The golf ball of claim 1 , wherein the amount of the benzoquinone present in the rubber composition is at least 0.2 parts by weight per 100 parts of the base rubber.

6. The golf ball of claim 1 , wherein the core is a single layer.

7. The golf ball of claim 1 , wherein the core comprises an inner core layer and an outer core layer, and wherein the inner core layer is formed from the rubber composition.

8. The golf ball of claim 1 , wherein the core comprises an inner core layer and an outer core layer, and wherein the outer core layer is formed from the rubber composition.